Adding VST Support to Linux Audio Applications

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1 Adding VST Support to Linux Audio Applications Paul Davis Lin ux Audio System s (b ased on work b y Kjetil Mattheu ssen, Torben Hoh n and Paul Davis)

2 What is VST? Technology from Steinberg An audio/midi plugin API Support for win32/x86, MacOS9, MacOS X Plugins roughly divided into a DSP core and an optional customized GUI

3 The Problem VST plugins for Windows are packaged in a win32/x86 file format VST plugins for Windows make win32 API calls Linux does not (natively) support either of these.

4 The Solution Wine WINdows Emulator? Wine Is Not an Emulator? Wine provides 95%+ of the win32 API by translating it into native linux library and OS calls. Traps systems calls, exceptions 1,000,000+ lines of code, +25%/month

5 The Problem, Part II Wine is intended for running win32 programs We have win32 plugins We want to use them in a native Linux application We are not alone: Mono, game people using DirectX, others.

6 The Kjetil is not Black Kjetil Mattheussen did the first open source implementation of VST support Created a win32 application Compiled it with winebuild Result: a native Linux app that can load win32.dll's (VST plugins) Connect to other Linux programs with a client/server protocol

7 VSTserver Features Isolates VST and win32 code from host Plugin can crash without affecting the host Plugin cannot access host data structures Sweet! But...

8 Problems with VSTserver 2 context switches to run a plugin's process() callback Doesn't scale Imagine a session with 2-4 plugins on most of 24 tracks.

9 A Different Approach Run VST plugins in the same process as the host Must be able to load and run win32 code Don't use wine(1) or winebuild Mono's shared wine hack

10 Mono and setjmp WinMain () { longjmp (jmpbuf, 1); } if (setjmp (jmpbuf) == 0) { wine_init ( run me ); /*NOTREACHED*/ }... now have a win32-ready thread...

11 The Problem, Part III The Mono hack doesn't support threads All audio apps require threads Therefore...

12 Win32 Thread Ugliness All thread systems need some way to identify the current thread win32/x86 uses the %fs register for comparison, NPTL and later linuxthreads use %gs Contents point to a block of information allocated from the processor Local Descriptor Table (LDT) Any thread running win32 must have %fs point to a valid LDT entry

13 Ugly? Or Just Windows? Wine takes over thread management Wine starts before the application With a native Linux application, there are threads created using the native thread API Wine doesn't know about these threads, thus %fs is not set up wine_adopt_thread ();

14 How We Do It Allocate a special proxy thread when wine is started, using win32 thread API Thread waits for notifications of new linux threads Tells Wine about them, passes back %fs information Linux thread has %fs set, can now execute win32 code.

15 The GUI Most VST plugins come with their own custom editor Native win32 or vstgui calls its all the same to us Need an entire win32 event loop running the host. Window management...

16 Window Management 1 the win32-created window has no WM decoration the win32 thread is an Xwindow, but no X toolkit knows about it linux apps can't manage it as if it was a normal toolkit window we need to adopt the window XReparentWindow

17 Window Management 2 we wait for the window to be created use whatever wrapper around XReparentWindow a toolkit provides for GTK+, GtkSocket, gtk_socket_add_id(), gtk_socket_steal() ideally, use XEMBED extension not supported by wine

18 Window Management 3 after reparenting, when the window is moved, the win32 GUI layer doesn't know coordinates of mouse events are wrong have to forward the correct kind of XEvent to the win32 layer in GTK+, catch configure events, synthesize a new XConfigure event, send to the XWindow underlying the win32 window.

19 Writing a Host you need to: (1) supply an audiomaster callback to handle requests from the plugin (2) probably augment the FST data structures with something application specific (think LADSPA) (3) take care of window management (configure events, etc.)

20 Plugin Discovery Suprise its really slow (loading multiple win32.dll files) fstconfig builds caches of basic VST plugin info in foo.fst fst_get_info (dllname) will get (and if necessary re-build) info for a.dll much, much, much faster LRDF?

21 fst_init (); fst_load (); fst_unload (); fst_instantiate (); fst_close (); fst_run_editor (); fst_destroy_editor (); fst_get_info (); The API

22 Success Stories Kontakt, Battery from Native Instruments Crystal Lots and lots of small, interesting and useful plugins

23 where to begin? Problems

24 Without Whom Torben Hohn Kjetil Mattheussen The Mono crew for getting us started Alexandre Julliard, Mike Hearns, Mike McCormack and Chris Morgan of the Wine project for advice and guidance. Smartelectronix for open source plugins. Steinberg. Hmm. Yes.

Fall 2014:: CSE 506:: Section 2 (PhD) Threading. Nima Honarmand (Based on slides by Don Porter and Mike Ferdman)

Fall 2014:: CSE 506:: Section 2 (PhD) Threading. Nima Honarmand (Based on slides by Don Porter and Mike Ferdman) Threading Nima Honarmand (Based on slides by Don Porter and Mike Ferdman) Threading Review Multiple threads of execution in one address space Why? Exploits multiple processors Separate execution stream